In a semiconductor device, a contact hole is used to form an electrical connection between a contact region in a substrate and an associated contact. One approach to form the contact region into the substrate is to perform a silicidation process through the contact hole. However, as semiconductor devices continue to be scaled down, a critical dimension (CD) of each contact region is increasingly shrunk, and undesired effects such as encroachments may occur at the contact regions during the silicidation process. Accordingly, it is more and more difficult to form a contact region into a predetermined portion of the substrate by the silicidation process through the contact hole.